Yeah it's the food but there also wasn't electricity giving us 24/7 wake behaviors. We used to follow the sun for sleep/wake and that circadian rhythm when disrupted damages the immune system. It's more a thing than the does.

Al principi del segle XX l'esperança de vida no arribava als 60 anys, que no us enganyin amb falòrnies!

On average people lived shorter because many died early, but bunch of people still lived into old age. And nowadays people are developing heart disease even in their 50s whereas heart disease was extremely rare in any age group, even in 50s and beyond.